Malaysian police said on Thursday that teenager Nora Quoirin died from internal bleeding likely caused by hunger and stress.
They added that the autopsy had not found evidence of sexual assault or that she had been the victim of a kidnapping.
Negeri Sembilan state police chief, Mohamad Mat Yusop, said the post-mortem also revealed that the teenager had died two or three days before her body was found.
Small scratches on her legs were discovered with samples taken and sent to the Chemistry Department for further testing, Mohamad also said, adding, however, that the pathologist had ruled that they had not contributed to her death.
Nora Quoirin, 15, who suffered from learning disabilities went missing on August 4. Her unclothed body was discovered on Tuesday near a stream some 2.5 km away from the Dusun resort in Seremban where she had been staying with her family for a holiday.
"Nóra is at the heart of our family. She is the truest, most precious girl and we love her infinitely. The cruelty of her being taken away is unbearable," her family said in a statement on Wednesday.
"Our hearts are broken," they added.
The nine-day search for the missing teenager involved more than 350 officers with authorities from Ireland, France and Britain — the Quoirin family resides in London — also providing assistance.
France announced on Wednesday that it had opened a criminal probe for kidnapping. The country, from where Nora Quoirin's father comes, often launches investigations involving French citizens abroad.